It’s Apache.
So will that delete the old certificates from my home server? I can’t seem to wrap my mind around the mechanism that prevents certificate stealing. How would letsencrypt know the new DO server was allowed to call itself example.com??

So will that delete the old certificates from my home server? I can’t seem to wrap my mind around the mechanism that prevents certificate stealing. How would letsencrypt know the new DO server was allowed to call itself example.com??

Let’s encrypt use DNS or HTTP validation to confirm… Hense if you point the domain to server, it would pass the validation.

It depends on your challenge type. The HTTP-01 challenge requires you to place a specific file with specific contents at .well-known/acme-challenge/ on your web server. The DNS-01 challenge requires you to create a DNS TXT record at _acme-challenge with specific contents.